The present invention relates to a semiconductor rectifying module.
In order to rectify alternating current, presently diode or thyristor hybrid or integral rectifying bridges are used. In general, as disclosed for example in U.S. Pat. No. 3,654,527, a diode rectifying bridge is a metal base operating as a heat removal, on which two metal plates are mounted as current leads by means of a spacer of dielectric heat conducting material, which as a rule is ceramic or organosilicon compound. At least one diode is mounted on every metal plate, and the diode connection of different plates is made anti-parallel. The isolation of diode elements both for separate and group versions (hybrid or integral) is performed by means of grooves on upper and lower surfaces hampering the rectifying module mounting. In this case the optimal configuration of the grooves with respect to the breakthrough voltage is not determined. In case of hybrid version, the isolation between separate elements is performed by air gaps resulting in essential increase of the module size as well as in decrease of mechanical strength.
In the case of anode bridges, there are no group diodes mounted with the cathodes on one plate, and cathode group diodes with their anodes on the other plate, and their contact surfaces are located in one plane. In the case of thyristor controlled modules as disclosed for example in European patent application 0015053 or U.S. Pat. No. 4,313,128, since control areas are located on the cathode side, the thyristor element anode surfaces are directed to the plates. Since the rectified current has to be supplied to the cathode of one thyristor group and to the anode of the other thyristor group, in the above described method of mounting of thyristor elements the supply of the current to be rectified and the output of the rectified current to the thyristors of the anode group is complicated and requires special constructions of current leads and collectors which results in a more complicated constructions, its lower reliability, its higher mass and size. The isolation of separate thyristor elements is usually performed by means of air gaps, which increases the dimensions and reduces reliability since conductive agents, such as water can penetrate between the elements.
As for mass and dimensions, thyristor modules are desirable with anode group thyristors mounted with the cathodes on a common plate and cathode group thyristors with anodes mounted on a common plate, as for example in a diode rectifying bridge disclosed in U.S. Pat. No. 3,654,527. In this case a version of the Japanese patent application 63-61786 can be utilized. However, for an anode group it is necessary to use thyristor elements mounted with their cathodes at the base. In this case there is a problem for the thyristor element to be controlled and for the p-n junction to be reliably isolated. One way to solve this problem is to provide the thyristor controlled from the anode side with a region of the electron type as a gate, as disclosed in British Patent 1,185,667. The presence of the fifth layer leads to uncontrolled turning on during the commutation which is the effect similar to the dv/dt.sub.com effect in triacs. Another version is a reverse p-n-p-n structure with the gate located in the bottom plane, which however complicates assembling and lowering the switching voltage since the reverse p-n-p-n structure does not allow creating a needed strength factor on the surface due to the special protection coat thickenings. This problem cannot be solved by means of p-n-p-n structure with the groove and an isolating p-layer as disclosed in the Japanese patent application 63-61786. Here, as well as in the case of U.S. Pat. No. 4,131,128 the groove optimal configuration with respect to the breakthrough voltage is not determined.
As for the reverse rectifying bridges they have to use bidirectional thyristors such as triacs or symistors as disclosed in British Patent 1,186,667. However, these devices have different current values for forward and reverse polarities and the reverse control current can essentially exceed the control current of a conventional thyristor. For using in rectifying circuits, optothyristor pairs are desirable, with a photothyristor as a photodetector and a semiconductor light emitting diode as a light source. In this case an electrical decoupling (isolation) between the control circuit and the main circuit is obtained. There are many solutions with the use of photothyristors controlled from the cathode side, as disclosed for example in German Patent 2,951,916. There is no information about a second group of photothyristors controlled from the anode side, and it is believed that the reason is that the anode side control requires more power.
As for reverse rectifiers with an isolated input, optosymistors with optrons as rectifying elements should be used. In this case a photosymistor which is a bidirectional switch is used as a photodetector controlled by light from one plane side, as disclosed in the publication Y. A. Evseev, A. N. Dumanevitch "The New Types of Symmetrical Thyristors", World Electrotechnical Congress Reports, Section 5A, Report 42, Moscow, 1977. A semiconductor light emitting diode is used as a light source. The problem of low control power with maintaining dynamic characteristics is even more complicated for photosymistors as compared with photothyristors.